Novel transport and recombination processes in semiconductors

This report describes work on spin dependent recombination processes, electron injection from point contacts into semiconductors and the Quantization of Hall resistance in strong magnetic fields. The work on spin dependent processes has identified spin dependent recombination and generation processes as well as a non-resonant magnetic field effect centered at zero magnetic field. This effect clearly has the same cause as the resonant generation and recombination processes. Resonance effects were constant over a wide range of frequencies confirming theoretical predictions that this was the case. Work on two dimensional systems has concentrated on the two terminal properties in the regime of quantized Hall resistance. The inversion layer has been shown to behave as a voltage source with quantized impedance. Frequency measurements have shown that fractional quantization can be introduced as integer quantization is destroyed. The frequency dependence is shown to be dependent on sample length, this being the maximum localization length which can occur. Point contact injection from Al and Ag point contacts into Si has been investigated, it is shown that instabilities occur due to coupling between electronics and plasmons.